Update README.md

Add detailed README with Xpdf installation instructions and script usage guide

README.md

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-# invoice_renamer
-Powershell script to rename invoices based on who they're being sent to
+# Rename PDF Invoices by "Bill to" Name
+
+This repository contains a PowerShell script that automatically renames PDF invoice files based on the content found under the "Bill to" section within each PDF.
+
+The script is especially helpful for batch-renaming large numbers of invoice PDFs quickly and consistently.
+
+## How It Works
+
+- Extracts text from each PDF using the `pdftotext` utility from Xpdf tools.
+- Uses regex to reliably find the "Bill to" section and captures the subsequent line as the customer name.
+- Renames the PDF file to a clean, safe filename formatted as `[Customer Name] 2025 calendar ad invoice.pdf`.
+
+## Prerequisites
+
+You must install the Xpdf command-line tools (which include `pdftotext.exe`).
+
+### Installing Xpdf CLI Tools
+
+1. **Download Xpdf**:
+   - Visit [Xpdf Download Page](https://www.xpdfreader.com/download.html).
+   - Under the "Xpdf command line tools" section, download the ZIP file (`xpdf-tools-win-*.zip`).
+
+2. **Extract Files**:
+   - Extract the downloaded ZIP file to a convenient location (e.g., `C:\xpdf-tools`).
+
+3. **Add Xpdf to Windows PATH**:
+   - Press `Win + R`, type `SystemPropertiesAdvanced`, and press Enter.
+   - Click on "Environment Variables".
+   - Under "System Variables", select `Path`, then click "Edit".
+   - Click "New" and add the path to your extracted Xpdf directory (e.g., `C:\xpdf-tools\bin64`).
+   - Click OK on each dialog to apply the changes.
+
+4. **Verify Installation**:
+   - Open a new PowerShell or CMD prompt and type:
+     ```shell
+     pdftotext.exe -v
+     ```
+   - If installed correctly, this command should display the version information.
+
+## Using the Script
+
+### Run the Script
+
+1. Place the script file (`RenameInvoices.ps1`) in the directory containing your PDF files.
+2. Open PowerShell in that directory.
+3. Execute the script:
+   ```powershell
+   .\RenameInvoices.ps1
+   ```
+
+### Script Behavior
+
+- The script scans all PDFs in the current directory.
+- It outputs verbose messages during file renaming.
+- Provides warnings for:
+  - Files where "Bill to" information is missing.
+  - Potential filename conflicts.
+
+## Customization
+
+- Modify the `$newFileName` format if you prefer a different naming convention.
+
+## Contributing
+
+Feel free to open issues or submit pull requests to improve this script further.
+
+## License
+
+This project is open-source and free to use. See the repository license for more details.